It is common in the steel making industry when faced with high cost of scrap as feed material for steel making furnaces to turn to other sources for use as raw material in the steel making process. A particularly attractive raw material is reduced iron which has been produced by the direct reduction of iron oxides. The direct reduced iron oxides (known as DRI) are formed as pellets and/or briquettes and are particularly useful as a feed material to electric arc steel making furnaces.
One of the most common processes employed for the direct reduction of iron oxides resides in the external reformation of natural gas so as to produce a reducing gas for the direct reduction process. Typical processes are disclosed in U.S. Pat. Nos. 3,764,123; 3,816,101; and 4,046,557. In accordance with these processes, a direct reduction reactor is fed with a reducing gas generated in external reformers. The external reformers carry out a catalytic conversion process for converting natural gas and an oxidant to a reducing gas having a high H.sub.2 +CO content. The reducing gas produced in the reformers is thereafter fed to the direct reduction reactor wherein the reformed gas contacts the iron oxide materials at a temperature of about 820.degree. C. so as to reduce the metal oxides to a direct reduced iron product having a metal content of at least 85% Fe. In accordance with the processes, the reduced gases produced in the reformers are cooled down to a temperature of below 850.degree. C. prior to introduction in the reactor. The oxidation degree of the reducing gas produced in the reformers is less than or equal to 0.07 wherein the oxidation degree n.sub.O is expressed as follows: ##EQU1## It is necessary to cool the reducing gas produced in the reformers prior to feeding same to the reduction reactor so as to control the temperature within the reduction reactor thereby avoiding sticking of the reduced iron in the reduction zone which is detrimental to the efficient operation of the process.
In order to increase the production of existing facilities employing the processes discussed above, one must increase the capacity of the external reformers so as to increase the quantity of reducing gas fed to the reactor. When adding additional external reformers, it is necessary to enlarge existing ducting, etc., of the overall facility. The investment costs and operating costs involved with increasing the capacity of external reformers is significant.
Naturally, it would be highly desirable to provide a method for retrofiting existing direct reduction facilities and modifying existing direct reduction process conditions so as to allow for an increase in the quantity and quality of the reducing gas and correspondingly increase the overall production capacity of existing facilities without the necessity of increasing the existing external reformers.
Accordingly, it is a principal object of the present invention to provide a process for improving the production capacity of conventional direct reduction facilities without the necessity of providing additional external gas reformers.
It is a particular object of the present invention to provide a retrofit direct reduction facility which allows for increased production of direct reduction without requiring increased capacity of external reformers existing within the facility.
It is a further object of the present invention to provide a modified direct reduction process and retrofit direct reduction facility as aforesaid wherein production capacity is increased while at the same time recognizing a reduction in energy consumption of the facility.
Further objects and advantages of the present invention will appear hereinbelow.